12... c6e7 The knight returns to defend the pawn on d5 and also makes it possible to advance the pawn to c6 (which allows the knight to be repositioned later) or even to c5, as will happen in the game. The problem with this move is that it makes it easier for White to advance a pawn to c4 or e4, due to the knight's temporarily passive position. 13. e2e3 Preparing the c3-c4 advance, one of White's plans. Perhaps it would even be better to play the other possible plan, which is to advance the pawn to e4, either now or after 13.Qa4. 13... c8e6 The bishop is developed while keeping an eye on c3-c4. 14. d1a4  14... a7a6 